Since the beginning of this century, the global consumption of unrenewable energy sources such as fossil energy sources, for example, coal and oil, and nuclear energy is growing rapidly. As fossil energy sources have arrived at or are approaching to their peaks of supply, mankind has to face the most vital turning point in history, due to both the incoming energy crisis and the global warming which is regarded as the prime cause of various synoptic disasters around the world in recent years and may be attributed largely to the warming gas, i.e. carbon dioxide, most of which originates from fossil energy sources. Therefore, new renewable energy sources must be developed and utilized so as to ensure the continuing existence and sustainable development of human beings.
Great importance has been attached to renewable energy resources all over the world. Biomass derived ethanol fuel is becoming a member of the technical field of liquid fuel, and the processes of producing ethanol fuel from starch and cellulose are under modification and improvement. Particularly, after we developed a technology for rapid pretreatment of cellulosic biomass and a corresponding novel production process (Patent Application No. 200610008062.2, PCT/CN2006/001129), the cost of producing ethanol fuel from cellulosic biomass in industrial scale is expected to be comparable to that of starch derived ethanol fuel, and a booming development of the production of ethanol fuel from cellulosic biomass is promising.
The current process of producing ethanol liquid fuel by fermentation of the starting material cellulosic biomass or starch comprises four major steps as follows: the first step involves pretreatment, the second step is the hydrolysis of the high molecular polymer of saccharide into monosaccharide, the third step is the fermentation of monosaccharide into ethanol, and the fourth step is the separation and dehydration of ethanol to give ethanol fuel. The production of biomass derived butanol fuel shares the same procedure.
The loss of organic carbons in the production process via fermentation is tremendous for both ethanol and butanol. When hexose is used as the monosaccharide, one third of the organic carbons are converted into inorganic carbons of carbon dioxide during fermentation. When pentose is used as the monosaccaride (xylose), sixty percent of the organic carbons are converted into inorganic carbons of carbon dioxide during fermentation. As to another pentose, namely arabinose in cellulosic biomass, it is totally lost due to the lack of good zymogens that can be used for its conversion. In addition, ethanol fuel is produced at high cost owing to the difficulty in dehydration of ethanol. In order to make better use of biomass energy sources, it is necessary to develop a new production process which can avoid the loss of organic carbons.

With coal being far more than oil in terms of storage on the earth, it may be predicted that a wide range of coal chemical engineering projects and production bases will rise in full scale, and a lot of hydrogen will be produced as the byproduct. Meanwhile, as the technology of producing hydrogen from coal will be further developed, lower cost will be achieved. Moreover, along with the development of other scientific technologies, the technology of directly producing hydrogen using solar energy will be gradually improved, and the cost will be lowered steadily. New economical and reliable technologies of power production will emerge one after another, resulting in the rapid reduction of the cost for the production of hydrogen by electrolysis. However, it is rather difficult to transport and utilize pure hydrogen. Storing hydrogen in hydrocarbon compounds is one of the best choices to store hydrogen. Thus, one of the most important applications of hydrogen will possibly be the production of biomass liquid fuel and other applications in the field of biomass.
Another consideration is the final cost effectiveness of cellulose hydrolases. Although cellulose hydrolases have already been much more cost effective than previous years thanks to the rapid development of biological technologies and the hard work done by scientific and technical workers in recent years, their cost effectiveness is still rather poor as compared with that of starch hydrolases. It needs further consideration as to whether it is possible or necessary to develop a cellulose hydrolase with high effectiveness. The fact is that cellulosic biomass is a basic energy source upon which the living of animal on the earth relies, and it evolves gradually to a life which is resistant to all cellulose hydrolases. If a super microorganism capable of breaking up cellulosic biomass readily were made successfully, the doomsday of higher animals and plants would come once this super microorganism happened to break into nature out of man's carelessness. Therefore, it is not possible that a cellulose hydrolase with perfect effect will be developed in near future, and the cost of cellulose hydrolases will not be decreased to the level of starch hydrolases. Thus, it is necessary to develop alternative processes of degrading cellulose.
Dehydration and polymerization of monosaccharides and polyols in the presence of acid catalysts are among the most common organic reactions in organic chemistry. The novel process of producing liquid fuel as disclosed in the present invention takes advantage of the undesirable side reactions of saccharides and polyols under acidic conditions, which reactions the scientific and technical workers previously made every effort to avoid. For example, hexose is converted into methylolfurfural under acidic conditions, and pentose is converted into furfural under acidic conditions, etc. These carbonyl compounds will further polymerize to produce organic compounds containing more carbons.